Quote ="Ferocious Aardvark"Nope.
It is twice as likely to be a boy.
We know the parents have 2 children.
We know only that one of them is a girl.
Here are the only possibilities of what could have happened
1. Boy - Boy
2. Boy - Girl
3. Girl - Girl
4. Girl - Boy
We can eliminate no. 1 immediately, can't be boy-boy because one of the children (Myrtle) is not a boy.
But the other 3 remaining possibilities are equally likely. And in 2 out of 3, the sibling is a boy.
QED'"
2 and 4 are exactly the same result you are trying to say 10 + 5 = 15 but 5 + 10 doesn't = 15.
So only two possibilities which are equally likely so it's a 1 in 2 chance of being a boy.